Method for the reformation of fuels, in particular heating oil

ABSTRACT

The method for the reformation of fuels, in particular of heating oil ( 20′ ) and of another liquid fuel is carried out using an oxygen containing gas ( 5   a,    5   b,    21′, 22′ ). The method includes the following steps:  
     formation of a fuel/gas mixture by dispersing of the fuel in a jet of the oxygen containing gas ( 21′ );  
     additionally an admixture of gas of a return flow ( 3   b ) and vaporization of the dispersed fuel;  
     generation of synthesized gas from the gas mixture by means of partial oxidation and also reformation processes by heterogeneous catalysis;  
     branching off of the produced synthesized gas into a product flow ( 3   a ) and the return flow ( 3   b ) for a recirculation; and  
     a regulated extraction of heat from the return flow for the setting of a predetermined temperature of a catalyst support ( 10 ) on which the heterogeneous catalysis takes place.

[0001] The invention relates to a method for the reformation of fuels,in particular of heating oil or another liquid fuel, preferably for thepurpose of obtaining electrical and thermal energy by means of hightemperature fuel cells. The invention also relates to apparatuses forcarrying out the method and also to a plant with fuel cells in which themethod of the invention is used.

[0002] The reformation of hydrocarbons, which are for example present inthe form of fuel gas or vaporized heating oil, can be carried outcatalytically at around 800° C. with the admixture of water in vaporform and a supply of heat. During the reformation carbon monoxide andhydrogen arise which, as educts, can be used for electrochemicalprocesses in high temperature fuel cells, for example in the battery offuel cells as is known from EP-A-0 780 917 (=P.6719). This batterycontains a cell block with fuel cells which is surrounded by a heatinsulating sleeve. An afterburning space is located between the sleeveand the cell block. A reformer (also termed a pre-reformer) which issuitable only for the preparation of a gaseous fuel is arranged in thesleeve. It is connected to a heat exchanger by means of which the heatrequired for the reformation processes can be supplied to it fromexhaust gases.

[0003] When air or another oxygen containing gas which is composed of aninert component and of a component consisting molecular oxygen O₂ isadmixed to the hydrocarbons a partial oxidation takes place in parallelto the endothermic reformation processes, the partial oxidation isexothermic and water arises as a reaction product. The water formed bythe partial oxidation serves as an educt of the reformation. Anadmixture of water is thus no longer required or only partly required,which is advantageous since water is expensive having regard to thedemands made on its purity. However a problem arises when thereformation is carried out together with a partial oxidation, as thefollowing explanations show:

[0004] The reformation processes are carried out by a heterogeneouscatalysis in a catalytic converter with a uniform structure. Thecatalytic converter consists of a catalyst support, on the surface ofwhich the catalytically active material, namely a platinum material (inparticular platinum, rhodium or palladium), nickel or a mixture of suchmetals is applied. The oxidation which takes place simultaneously doesso much more quickly then the endothermic reformation reaction; it thustakes place in an inlet region of the catalytic converter in which hightemperatures arise as a result of the heat output through the oxidation.These temperatures can result in a deactivation of a catalyticallyactive metals, for example by vaporization and thus damage to thecatalytic converter.

[0005] The object of the invention is to provide a method for thereformation of a fuel, in particular heating oil or another liquid fuelin which a partial oxidation is carried out simultaneously with thereformation but in which a damaging effect of the exothermic processeson the catalytic converter is avoided. This object is satisfied by themethod defined in claim 1 in that with the named measure of a return ofsynthesized gas the temperature in the inlet region of the catalyticconverter can be reduced so far that thermal damage is prevented.

[0006] The method for the reformation of fuels, in particular heatingoil or another liquid fuel is carried out using an oxygen containinggas. The method comprises the following steps:

[0007] formation of a fuel/gas mixture by dispersing of the fuel in ajet of the oxygen containing gas;

[0008] additionally an admixture of gas of a return flow andvaporization of the dispersed fuel;

[0009] generation of synthesized gas from the gas mixture by means ofpartial oxidation and also reformation processes by heterogeneouscatalysis;

[0010] branching off of the produced synthesized gas into a product flowand the return flow for a recirculation; and

[0011] a regulated extraction of heat from the return flow for thesetting of a predetermined temperature of a catalyst support on whichthe heterogeneous catalysis takes place.

[0012] The dependent claims 2 to 5 relate to advantageous embodiments ofthe method of the invention. The subject of claims 6 to 9 is anapparatus for carrying out the method. Claim 10 relates to a plant witha battery of high temperature fuel cells which are operated with heatingoil reformed in accordance with the invention.

[0013] In the following the invention will be explained with referenceto the drawings. There are shown:

[0014]FIG. 1 an apparatus for carrying out the method of the invention,

[0015]FIG. 2 a diagram with a temperature profile which results withpartial oxidation and simultaneous reformation in a catalytic converter,

[0016]FIG. 3 a plant with a battery of high temperature fuel cells andan apparatus in accordance with the invention for the reformation ofheating oil,

[0017]FIG. 4 a particular two material nozzle and

[0018]FIG. 5 a second embodiment of the apparatus of the invention.

[0019] The method of the invention can be carried out with the apparatusshown in FIG. 1. A heating oil/gas mixture is sprayed into the apparatus1 by means of a two material nozzle 2 which has a central infeed 20 forheating oil 20′, a lateral infeed 21 for an oxygen containing gas 21′and a nozzle tip 23. In this connection a further part flow 22′ of theoxygen containing gas is united with the heating oil/gas mixture via aninfeed 22 and a ring-like nozzle 13. (The method of the invention canalso be carried out without this part flow.) At the outlet of the nozzle13 the emerging jet brings about a depression by which the gas of a hotreturn flow 3 b is sucked in. Heat is supplied to the dispersed heatingoil, which can be fed cold into the two material nozzle 2, by mixing ofthis hot gas with the jet of the nozzle 13 so that the heating oil isvaporized. A radiation of heat through the hot catalytic converter 10contributes to heating up of the dispersed heating oil so that the heatrequired for the vaporization does not have to be supplied solely by thereturn flow 3 b.

[0020] The two material nozzle 2 is arranged at a distance remote fromthe catalytic converter 10, with the distance to an entry surface 100being sufficiently large that an adequately long dwell time exists forthe vaporization of the heating oil prior to the inlet and that themixture enters into the catalytic converter 10 distributed over the fullentry surface 100. The catalytic converter 10 is located in a firstcylindrical tube 11. A second cylindrical tube 12 forms part of an outerwall of the apparatus 1. The catalytically produced synthesized gas isbranched off below an outlet surface 101 into a produt flow 3 a and thereturn flow 3 b. The product flow 3 a leaves the apparatus 1 through anoutlet tube 29. The return flow 3 b, driven by a pressure drop whicharises as a result of the depression at the nozzle 13 is guided upwardlythrough a recirculation gap, which is a ring space between the two tubes11 and 12. Heat is extracted from the return flow 3 b by means of a heatexchanger 6. With a regulated extraction of heat the temperature T_(K)of the catalytic converter 10 can be influenced so that, for example,the average temperature adopts a pre-determined value.

[0021] The temperature T_(K) has a profile as is qualitativelyillustrated in the diagram of FIG. 2. The x-axis, the direction of whichis drawn in in FIG. 1, extends in the main flow direction of thecatalytic converter 10. The left hand line 100′ of the diagramcorresponds to the inlet surface 100, the right hand line 101′corresponds to the outlet surface 101. As already mentioned thetemperature has a maximum in the inlet region as a result of theexothermic processes. The endothermic processes of the reformation bringabout a gradual reduction of the temperature after the maximum. Thetemperature interval ΔT quoted must lie within an interval, the limitsof which are given by a required minimum temperature of around 700° C.and a maximum permissible temperature of around 1000° C. This conditioncan not be satisfied without the measure of the invention.

[0022] Thanks to the return flow 3 b the temperature interval ΔT of thetemperature profile is smaller and the average temperature can be setlower. The reduction of ΔT results for two reasons: a) The partialpressure of the heated oil vapor is reduced by the returned gas(increase of the proportion of inert gas). b) Water is already madeavailable in the inlet region of the catalytic converter (water whicharises in the process) for the reformation processes and thus produces aheat sink. These two reasons also have the advantageous effect that sootformation in the catalytic converter 10 is suppressed.

[0023] Having regard to the recirculation, the packing should have astructure which produces the smallest possible flow resistance. Anordered packing is of advantage, the structure of which is a honeycombstructure with parallel flow passages or a structure with wave-shapedfoils and open, crossing, flow passages (“crossed channel structure”). Areticular foam structure or a structure of a three-dimensional braid isalso possible.

[0024] The plant 9 shown in FIG. 3 comprises a battery 9′ in the form ofa stack of planar ring-line high temperature fuel cells 90 and anapparatus 1 in accordance with the invention for the reformation ofheating oil. Apart from the fuel cells 90 the following components canbe seen: a sleeve 93 which has a non-illustrated internal constructionby means of which environmental air (inlet 92) is preheated duringoperation and uniformly distributed to the cell stack; an afterburningspace 94 between cell stack 9′ and sleeve 93 from which waste heat isled away via a heat exchanger 95 (transfer of heat Q to a water circuit,for example); a fan 96 with which the exhaust gas is sucked away andconveyed into a chimney; pole 98 for the transmission of electricalenergy E to a consumer.

[0025] Oxygen-containing gas forwarded by a pump 4 is fed into theapparatus 1 with the two partial flows 21′ and 22′. Environmental air 5a and/or exhaust gas 5 b from an afterburning of the fuel cell battery9′ is used as the oxygen containing gas. In a mixing apparatus 5 anideal ratio of environmental air 5 a and exhaust gas 5 b is produced.The product gas for the reformation is fed through the line 29 into acentral distributor passage 91 of the battery 9′.

[0026]FIG. 4 shows a special two material nozzle 2. This contains aheating cartridge 25 (electrical connections 25 a) with which theheating oil 20′ can be preheated to 400-420° C. to assist thevaporisation or to carry it out.

[0027] A second embodiment of the apparatus of the invention is shown inFIG. 5. For the return flow 3 b a second tube 7 is added to the firsttube 11 containing the catalytic converter 10, with the second tube 7being formed as a jet compressor. The second part flow 22′ and theoxygen containing gas is exploited as a driving medium. Synthesized gasis sucked in through a tube 70 by a driving nozzle 71. A subsequentdownstream tube element 72, in which a momentum transfer takes placefrom the driving medium to the synthesized gas, is formed as a heatexchanger 76 which corresponds to the heat exchanger 6 in the embodimentof FIG. 1. In a subsequent diffuser 73 deionised water 80 can be sprayedby a nozzle 8 into the return flow 3 b in order to utilize this fed-inwater 80 as a reaction component of the reformation processes and for acooling of the returned synthesized gas. The returned flow 3 b conveyedby means of the jet compressor 7 is distributed in the upper part of theapparatus 1 between an outer wall 11 a and a truncated cone-like wall13′ around a two material nozzle 2. The gas of return flow 3 b is unitedthrough the ring gap at the nozzle tip 23 with the heating oil/gasmixture emerging from the nozzle 2 and supplied to the catalyticconverter 10. The nozzle 2 can also be of the type shown in FIG. 4.

[0028] For the complete vaporization of the heating oil the return gasmust be sufficiently hot that a temperature of around 250-300° C. isachieved. When gas is recirculated with a temperature of 900° C. thenthe ratio of the return flow to the product flow must amount to around1:4. The higher the recirculation ratio is selected the more uniform isthe temperature profile in the catalytic converter. A ratio greater than1 is however not sensible for economic reasons, since the driving of therecirculation flow becomes expensive due to a high requirement of themomentum input.

[0029] The momentum required for the recirculation can be made availableby means of the reaction air in different ways. The reaction air can befed in in total via the two material nozzle, which results in a fineatomization that is associated with a relatively large energyrequirement. The reaction air can be fed in subdivided into primary andsecondary air, the primary air in the two-material nozzle and thesecondary air for example in a jet compressor. This second way ishowever more expensive apparatus-wise.

[0030] When carrying out an autotherm reformation in which water is usedas a reaction agent in addition to air the water can be exploited forthe regulation of the reaction temperature; the water can then beinjected into the recirculation gap.

[0031] The method of the invention can also be carried out with liquidfuels such as methanol, ethanol or “biodiesel” (vegetable oil). Moreovergaseous fuels (natural gas, liquid gas, biogas) can be used when themethod of the invention is modified somewhat (no vaporization of thefuel). With these fuels, which have a lower adiabatic temperatureincrease than heating oil, the conversion or turnover can be improved bya supply of heat—for example into the recirculation gap.

1. Method for the reforming of fuels, in particular of heating oil (20′)or another liquid fuel using a gas containing oxygen (5 a, 5 b, 21′,22′) comprising an inert component and a component consisting of oxygenO₂ the method including the following steps: formation of a fuel/gasmixture by dispersing of the fuel in a jet of the oxygen containing gas(21′); additionally an admixture of gas of a return flow (3 b) andvaporization of the dispersed fuel; generation of synthesized gas fromthe gas mixture by means of partial oxidation and also reformationprocesses by heterogeneous catalysis; branching off of the producedsynthesized gas into a product flow (3 a) and the return flow (3 b) fora recirculation; and a regulated extraction of heat from the return flowfor the setting of a predetermined temperature of a catalyst support(10) on which the heterogeneous catalysis takes place.
 2. Method inaccordance with claim 1, characterized in that the catalyst support (10)is an ordered packing or is built up from bulk fill of bodies with ahigh specific surface and in that the fuel/gas mixture is supplied bymeans of a two material nozzle (2) which is so formed and arranged thata depression at the tip of the nozzle (23) and a pressure drop resultingfrom this forms, the pressure drop being used at least partly as thedriving force for the return flow (3 b), with the packing having astructure, with regard to the recirculation, that produces the lowestpossible flow resistance, namely for example a honeycomb structure withparallel flow channels, a structure with wave-shaped foils and crossingflow channels, a reticular foam structure or a structure of athree-dimensional braid.
 3. Method in accordance with claim 1 or claim2, characterized in that deionised water (80) is sprayed into the returnflow (3 b) in order to exploit this fed in water as a reaction componentof the reformation process and for a cooling of the returned synthesizedgas.
 4. Method in accordance with one of the claims 1 to 2,characterized in that the oxygen containing gas (5 a, 5 b) is fed intothe process by means of a pump (4) and via at least two gas flows (21′,22′); and in that the first gas flow (21′) is used directly during thedispersion and in particular during a spraying of the heating oil (20′)and in that the second gas (22′) is fed into the return flow (3 b)through at least one driving nozzle (13, 71)
 5. Method in accordancewith one of the claims 1 to 4, characterized in that environmental air(5 a) and/or exhaust gas (5 b) from an afterburner (94) of a fuel cellbattery (9′) is used as a oxygen containing gas (21′, 22′).
 6. Apparatus(1) for carrying out a method in accordance with one of the claims 1 to5, characterized in that a catalytic converter (10) comprises a ceramicor metallic support structure and a catalytically active substanceapplied thereon which is located in a first cylindrical tube (11) and inthat a two material nozzle (2) for the generation of the heating oil/gasmixture (20′, 21′, 22′) is arranged at a distance from an entry surface(100) of the catalytic converter, with the distance being sufficientlylarge that an adequately long dwell time results prior to the entry forthe vaporisation of the heating oil (20′) and that the mixture entersinto the catalytic converter distributed over the full entry area. 7.Apparatus in accordance with claim 6, characterized in that the returnflow (3 b) is guided through a ring space between the first tube (11)and a second cylindrical tube (12).
 8. Apparatus in accordance withclaim 6, characterized in that a second tube (7) exists for the returnflow (3 b) and is arranged outside of the first tube (11), with thesecond tube being capable of being formed as a jet compressor (71, 72,73) and with a part (22′) of the oxygen containing gas being used as thedriving medium.
 9. Apparatus in accordance with one of the claims 1 to4, characterized in that the two material nozzle (2) is a combination ofa central nozzle for the fuel and a ring nozzle for the oxygencontaining gas (21′), with it being possible to integrate a heatingcartridge (25) in the central nozzle for the preheating or vaporizationof the heating oil.
 10. Plant (9) with a battery (9′) of hightemperature fuel cells (90) and an apparatus (1) in accordance with oneof the claims 6 to 9, characterized in that the apparatus and thebattery are connected by a line (29) for the product flow (3 a) of theapparatus and in that hydrogen and carbon monoxide of the product floware exploited as reducing reactants of electrochemical processes for thegeneration of electrical energy.